Solar cell products usually comprise a semiconductor substrate, preferably a silicon substrate with a photoactive p-n-junction, on a front surface being covered with a contact grid comprising stripes and finger-like structures, and a rear side with an electrical contact covering the entire rear side of the solar cell. The rear side is often prepared with screen printing methods.
In US 2009/0110808 A1 a manufacturing process is disclosed for preparing back contacts and surface fields on the rear side of a photovoltaic solar cell. Molten aluminum is used to form the contact regions by utilizing a spraying method, which may produce distributed point contacts and localized back surface fields for a passivated rear surface of the solar cell. The molten aluminium is sprayed on a dielectric layer arranged on the rear surface. The aluminium droplets can locally penetrate the dielectric layer and react with the silicon underneath.
The rear side metallization has a non-negligible influence on the efficiency of the solar cell. When forming the aluminum back contact, a degradation of the dielectric layer may decrease the efficiency of the solar cell by typically 1%-1.5%. Increasing the efficiency of solar cells has a great influence on the overall efficiency of a solar cell array comprising a great number of solar cells.